The invention relates to an anchor system of a concrete wall form with at least one locking device for an anchor rod of the anchor system, wherein the locking device has a screw nut element for screwing the anchor rod through a screw thread of the screw nut element.
Such anchor systems are used in formwork for steel-reinforced concrete structures. Concrete wall forms are made up of a formwork shell and its supporting elements, for example, longitudinal girders and tie beams. The two sides of a wall are each formed from one concrete form element, that is, a half-form, which are held together by anchor rods. The anchor rods are inserted through holes in the formwork shell and fixed at their ends to the elements supporting the formwork shell in such a way that the tensile force exerted on the anchor rods during concrete casting is held. Normally, the two ends of the anchor rods have threads onto which screw nuts are screwed as anchor fastenings. This determines the effective length of the anchor rod and therefore the thickness of the concrete wall. At the same time, the pressure exerted during concrete casting by the liquid concrete on the formwork shell is redirected via the screw nuts onto the anchor rods. The anchor rods are subject to tensile stress during this operation. Between the formwork shells, spacer elements are included in the volume of the concrete wall to be cast that can absorb the compressive forces that occur during concrete casting, it being ensured that these compressive forces do not influence the wall thickness in an unwanted way, that is, reduce it.
DE 197 54 366 C2 discloses an anchor system of a concrete wall form, in which a locking device is provided on one side of a concrete wall form. The locking device comprises a position fixture of a screw nut of the anchor system. The screw nut is fixed in position by locking screws fastened in a tie beam and extending transversely to the axis of the screw nut, preventing the screw nut fixed in position from being turned further. Due to the fastening of the locking screw on the tie beam, this position fixture also locks the screw relative to a half-form.
DE 103 36 414 B4 discloses an anchor system, wherein one very flexible locking device is provided on the rear of each of two form elements constituting a concrete wall form through which an anchor rod of the anchor system is inserted, by means of which both tensile and compressive forces exerted on the form elements can be held in such a way that the desired concrete wall thickness can be molded with precision.
With the known anchor systems, there are problems with inserting the anchor rod when the concrete wall form is erected, if the anchor insertion holes of the form elements with their formwork shells facing each other and forming the concrete wall are not sufficiently well-aligned opposite each other. Because the anchor rod is always inserted from the outside (as seen from the rear of a first form element) through the already erected form elements, the formwork erector who is positioning the anchor rod cannot see the anchor insertion hole of the second form element. The latter anchor insertion hole is found relatively easily but, with poorly aligned anchor insertion holes, the anchor rod extends obliquely with respect to the formwork shell of the form elements, making it very difficult to engage the thread of a locking device on the rear of the second form element. Moreover, if the anchor rod is oblique in this way, the locking devices cannot lie flat against the form elements around their entire circumference, which results in the forces that occur during concrete casting being transmitted to the locking devices concentrated at one point only, which places a heavy load on the locking devices.
DE 94 12 556 discloses a locking device for an anchor rod of an anchor system of a concrete wall form with a screw nut element for screwing the anchor rod, wherein a dome plate is provided that has a spherically formed plate section with an opening. The screw nut element is spherically shaped in such a way that it is held within the edges of the opening in a similar way to a ball-joint, in such a way that it can be moved, radial turning of the screw nut element in the opening being prevented by axial groove-type guides.
If the screw nut element is held in the dome plate in this way, the anchor rod screwed into the screw nut element can only move subject to very precise guidance. The dome plate therefore has to be exactly positioned relative to the anchor insertion hole in a formwork shell.
The object of the invention is to provide an anchor system for concrete wall forms, a locking device for the anchor system, and a concrete wall form that avoid the disadvantages of the prior art.
This object is solved by a locking device of an anchor system for concrete wall form elements, the anchor system having an anchor rod with an outer thread. The device comprises a fastening element cooperating with a back of a form element, a dome plate cooperating with the fastening element to fasten the dome plate to the back of the form element, the dome plate having a spherically shaved plate section defining an opening, a screw nut element having an inner opening with a screw thread for cooperation with the outer thread of the anchor rod, the screw nut element being disposed in the opening of the spherical plate section with radial play, the screw nut element defining a receptacle structured as a radial groove around an entire circumference thereof, the radial groove accepting edges of the spherical plate section opening and a tubular guidance facility aligned with the screw thread of the screw nut element and disposed at an end of the screw nut element facing a form element.